Study On Mechanical Properties And Electronic Properties Of Nc-Si:H Materials

Silicon is the basis material in the semiconductor industry.About 95%of materials in the semiconductor industry are silicone.Traditionally the monocrystalline silicon is the major materials.However,in the field of optoelectronic materials,the silicon is restricted because it is an indirect band gap material.In order to take full advantage of the rich resources and mature silicon technology,various methods are used to improve on the material.The silicon is prepared for the low-dimensional materials and doped with various forms to achieve its special function.In this paper,nano-Si:H films are fabricated by using highly hydrogen-diute silane as thereactive gas and activated with rf+ dc double-power sources,in a conventional plasma-enhance chemical-vapor-deposition system.The material is single or multiphase polycrystals and its crystals size if of the order of a few nanometers,which implies that about 50%of the material consists of a grain or interface region.It is apparent that the interface region between grains in the nanocrystalline material has a significant influence on the structure and properties of the materials.Using Hysitron Triboindenter of situ electrical and mechanical measurement technique,we obtained mechanical properties and contact current under constant voltage for phosphorus doped nano-Si:H films.We found there are several new mechanical properties and contact electronical properties of the films.It provides us important information to understand the structure and electronic properties of the films.From the view of quantum mechanics,we deduced the formula of transmission coefficient and tunneling current density through Schr(?)dinger equation directly.A model for nc-Si:H quantum wells for the phenomenon ofⅠ-Ⅴshock are observed at room temperature was developed.We have discussed a new model for the hydrogenated silicon-based materials periodic models for Si-H supercell.The electronic band structures of Si-H supercell are investigated by density functional theory calculations.Our results show that the Si-H supercell changes from indirect-gap semiconductor to direct-gap semiconductor with the increase of H content.It is found that the H atoms play a critical role in the band structure change.They can not only eliminate the defect states in the band gap, but also influence the Si-Si bonds.Thus,the interaction between Si 3s and Si 3s are weakened,whereas the interaction between Si 3p and Si 3p are strengthened.This result is confirmed by the TB theory,from which we considered that the direct-gap in the Si-H supercell is caused by the equivalent hybrid effect.Our findings indicate that the periodic models for Si-H compound alloy could be a novel material for photonic devices.